Agents inspect some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego.

Credit: Paul Caffrey/U.S. Immigration and Customs Enforcement/AP

U.S. Immigration Custom Enforcement Agent-In-Charge Derek Benner describes elements of a 1,760 foot cross-border tunnel used for drug smuggling in the Otay Mesa area of San Diego, Oct. 31, 2013.

Credit: Lenny Ignelzi/AP

U.S. Immigration and Customs Enforcement agents in a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.

Credit: Paul Caffrey/U.S. Immigration and Customs Enforcement/AP

A Border Patrol vehicle passes by the front of the industrial park office where a 1,760 foot cross-border tunnel used for drug smuggling was busted by federal authorities in the Otay Mesa area of San Diego Thursday, Oct. 31, 2013.

Credit: Lenny Ignelzi/AP

U.S. Attorney for the Southern District of California, Laura Duffy talks about the investigation leading to the discovery of a 1,760 foot cross-border tunnel in San Diego.

Credit: Lenny Ignelzi/AP

U.S. Attorney for the Southern District of California Laura Duffy, right, and an assistant walk down the loading dock ramp of a business where authorities found the 1,760 foot cross-border tunnel.

Credit: Lenny Ignelzi/AP

San Diego Police Chief William Lansdowne, second from left, and other law enforcement officials approach the door of an office where authorities discovered a 1,760 foot cross-border drug smuggling tunnel, Oct. 31, 2013.

Credit: Lenny Ignelzi/AP

Bales of some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.

Credit: Paul Caffrey/U.S. Immigration and Customs Enforcement/AP

Agents with bales of some of more than eight tons of marijuana and cocaine seized from a tunnel designed to smuggle drugs from Tijuana, Mexico, to San Diego, Oct. 31, 2013.